Oligosaccharide substrates for heparin sulfamidase.

Area of Science:

• Biochemistry
• Genetics
• Metabolic Disorders

Background:

• Sanfilippo A syndrome results from heparin sulfamidase deficiency, crucial for polysaccharide catabolism.
• Current assays use [N-35S]heparin, but it has limitations, necessitating alternative substrates.

Purpose of the Study:

• To evaluate heparin oligosaccharides as alternative substrates for heparin sulfamidase activity assays.
• To aid in the diagnosis and understanding of Sanfilippo A syndrome.

Main Methods:

• Synthesized and radiolabeled four distinct heparin oligosaccharides (tri- and pentasaccharides).
• Assayed enzyme activity using fibroblast sonicates from healthy individuals and Sanfilippo A patients.
• Determined optimal enzyme activity pH and compared kinetic parameters (Km, Vmax) with heparin.

Main Results:

• All four synthesized heparin oligosaccharides served as substrates for heparin sulfamidase in normal fibroblasts.
• Fibroblasts from Sanfilippo A patients exhibited minimal to no enzyme activity with these oligosaccharides.
• Optimal enzyme activity was observed at pH 4.4-4.5, with oligosaccharides showing higher Vmax than heparin.

Conclusions:

• Heparin oligosaccharides are viable and effective alternative substrates for heparin sulfamidase assays.
• These findings offer potential improvements for diagnosing Sanfilippo A syndrome and studying enzyme kinetics.